The present invention relates to microwave ovens and, more particularly, to a built-in microwave oven, designed to be installed in kitchen furniture at a predetermined position as an integral part of the kitchen furniture.
As well known to those skilled in the art, a microwave oven is an electrically operated oven using high-frequency electromagnetic waves that penetrate food, causing its molecules to vibrate and generating heat within the food to cook it in a short time. Conventional microwave ovens are classified into two types: a tabletop microwave oven designed to be seated on a table and a ventilation hood-combined microwave oven integrated with a gas range at the top portion of the gas range and collaterally acting as a ventilation hood.
In recent years, some kinds of electric kitchen appliances, such as gas oven ranges and pickled vegetable refrigerators, have been designed as built-in types in an effort to accomplish the recent trend of compactness of kitchen systems. Such built-in kitchen appliances preferably accomplish a desired harmony and a desired integration of the electric kitchen appliances with kitchen furniture.
In addition, conventional microwave ovens are typically designed to radiate high-frequency electromagnetic waves from a magnetron into the cooking cavity to allow the electromagnetic waves to penetrate food within the cavity, thus causing molecules of the food to vibrate and generating heat within the food to cook it in a short time. However, such a conventional microwave oven is problematic in that it undesirably has only a single heating mode with high-frequency electromagnetic waves, and so another type of microwave oven having a heater in addition to such a magnetron has been recently proposed and used. That is, microwave ovens, designed to use heat of a heater in addition to high-frequency electromagnetic waves of a magnetron so as to accomplish the requirement for a variety of heating modes and a variety of heating conditions, have been proposed.
The representative example of conventional heaters used in such microwave ovens having heaters in addition to magnetrons is a quartz tube heater. In the microwave oven having such a quartz tube heater as an additional heat source, heat from the quartz tube heater is forcibly convected within the cooking cavity to accomplish a convection-heating effect and to heat food within the cavity to a higher temperature.
Still another type of microwave oven provided with a halogen lamp capable of generating higher temperature heat and browning the surface of food has been proposed and used. In such a microwave oven, halogen lamps are installed at the top and bottom wall of the cavity of the oven, and radiate heat energy and light energy into the cavity, thus heating food within the cavity more quickly. When such halogen lamps are installed in microwave ovens, the lamps generate very high temperature heat, and so it is necessary to additionally install a cooling device for effectively cooling the halogen lamps and the surroundings of the lamps.
In accordance with the recent trend of built-in type structure of kitchen appliances, consumers require built-in microwave ovens. In such built-in microwave ovens, it is desired to install additional heaters, such as halogen lamps, in the ovens so as to accomplish a variety of heating modes and a variety of heating conditions of said ovens.
Such built-in microwave ovens are also set in kitchen furniture as integral parts of the furniture, with only the front walls of the ovens exposed from the front surface of the furniture to allow users to reach said front walls. Therefore, it is necessary to design such built-in microwave ovens to allow air to pass through only the front walls of the ovens.
During an operation of such a built-in microwave oven, the heater, in addition to the magnetron and the high voltage transformer installed within the machine chamber, generates high temperature heat.
It is thus necessary to cool the heater and the other heat generating elements of a built-in microwave oven using cooling air current. In such a built-in microwave oven, the air passage for the cooling air has to be provided at the front wall of the oven. However, such an air passage structure for built-in microwave ovens is completely different from that of the other types of conventional microwave ovens, and so it is impossible to use the conventional air passage structures in the built-in microwave ovens.
In addition, after the process of cooling the heater, magnetron and high voltage transformer during an operation of a built-in microwave oven, hot air is discharged from the external casing of the oven through the front wall of the oven to directly reach a user, thus making the user feel unpleasant. The hot air discharged from the front wall of the built-in microwave oven also damages or incapacitates elements set in the front wall.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a built-in microwave oven, which is designed to be installed in kitchen furniture at a predetermined position as an integral part of the kitchen furniture, and which allows cooling air for heat dissipation to pass through the front wall of the oven.
Another object of the present invention is to provide a built-in microwave oven, which is designed to desirably reduce the temperature of cooling air to a reasonable low point when the air is discharged from the external casing of the oven through the front wall of the oven after cooling the heat generating elements.
In order to accomplish the above object, the present invention provides a built-in microwave oven, comprising: a suction grille provided on the front wall of an external casing at a predetermined position for sucking air into the external casing; an exhaust grille provided on the front wall of the external casing at another predetermined position for discharging air from the external casing to the atmosphere; and means for forming air currents within the external casing while guiding inflow air from the suction grille to allow the inflow air to pass within the external casing prior to discharging the air from the external casing to the atmosphere through the exhaust grille.
In the above microwave oven of this invention, the suction grille and the exhaust grille are formed on the front wall of the external casing at predetermined positions. It is thus possible to provide effective built-in microwave ovens.
In accordance with another embodiment, the present invention provides a built-in microwave oven, comprising: a suction grille provided on the front wall of the external casing of the microwave oven at a predetermined position for sucking air into the external casing; an exhaust grille provided on the front wall of the external casing at another predetermined position for discharging air from the external casing to the atmosphere; at least one heating means used for heating food seated within a cooking cavity of the oven; a first air passage guiding a part of inflow air from the suction grille to the exhaust grille; a second air passage guiding a remaining part of the inflow air from the suction grille to the exhaust grille while allowing the air to pass by the heating means to cool the heating means; and means for forming air currents within the external casing by sucking the inflow air through the suction grille and by allowing the inflow air to pass through both the first and second air passages prior to discharging the air from the external casing to the atmosphere through the exhaust grille, whereby the first and second air passages are joined together at a position before the exhaust grille.
In the built-in microwave oven of this invention, it is possible to effectively reduce the temperature of exhaust air discharged from the external casing of the oven through the exhaust grille to a reasonable low temperature. Therefore, the exhaust air of the built-in microwave oven of this invention is almost completely free from thermally damaging or incapacitating the elements set on the front wall of the oven or undesirably making users standing or sitting in front of the oven feel unpleasant.